One of the many hazards of operating a motor vehicle is the probability of its windshield being hit by a stone or other small, hard object. Thanks to the safety glass, that is mandatory, the windshield usually withstands the shock of the hit, but quite often the outer layer of the safety glass is permanently pockmarked. The usual form of such a pockmark is a conical fracture with its apex at the surface where it was hit, and its base on the intermediate, resilient layer between the two layers of glass. This pockmark does not change the shape or decrease the strength of the safety glass, or limit its function as a windshield, but it is immediately apparent, visually, since the microscopic crevices or fissures between the newly-formed conical fracture and the rest of the outer glass layer provide reflecting surfaces that catch the light and distort images to make a virtual blind spot in the windshield at the fracture.
If such a pockmark or fracture is anywhere in the essential viewing area of the driver of the vehicle, it may be considered to be a safety hazard and the vehicle will not pass inspection. This would require a replacement of the windshield, which can be quite expensive, particularly with the modern cars whose windshields have become larger, more curved and more complex. Many, if not most of the windshields in use today, would cost several hundred dollars, so there is a very real need for some inexpensive way of repairing or neutralizing the effects of a pockmark.
Aside from enlarging the pockmark to remove the conical fracture and then filling the void with a transparent plastic of some kind, the only way of eliminating the effect of the reflecting surfaces is to fill the microscopic crevices or fissures with a transparent liquid that eliminates the reflecting characteristics of the sides of the fissure. If the liquid is self-hardening or can be hardened by heat or ultraviolet light, or the like, for example, and the surface of the glass at the pockmark is leveled and polished, the pockmark becomes virtually invisible, and is effectively cured.
A few methods have been devised for trying to get the various liquids that are available into the crevices of the pockmark. Basically, these methods apply the liquid to the surface of the windshield surrounding the pockmark, and then try to get the liquid to work its way into the crevices. One method uses a pointed tool to depress the conical fracture microscopically into the resilient layer between the two layers of glass so that the liquid can flow into the enlarged crevices. Another method uses a pointed tool to depress the conical fracture and provides an enclosed container to hold the liquid in contact with the area surrounding the pockmark, while a high frequency vibration is applied to accelerate the flow of the liquid into the crevices.
Still another method uses a combination of heat and pressure along with a pointed tool. After preparation of the glass, the liquid is held in a container against the pockmark and pressure on the liquid is alternately increased and decreased until the liquid appears to penetrate the crevices. This may involve pressure and vacuum cycles that are alternated until the air trapped in the crevices of the pockmark appears to be released, and the crevices appear to be filled.
While most of these methods teach the use of a sharp pointed tool or probe to displace the conical fracture, it should be noted that, in most cases, the probe is forced in by a screw with no control of the force on the point. It would be hard for the operator to know whether the pressure was insufficient or great enough to further damage the glass.
These methods and their corresponding apparatus may be effective for a reasonable percentage of the time and percentage of cases, however, the simpler of the methods provides no means for the removal of trapped air, and the more complex methods may or may not remove trapped air from the crevices. In any case, the more complex methods require relatively complex auxiliary equipment, including bracing structures to hold the apparatus against the windshield, and complex and prolonged cycles of treatment.
It is therefore an object of this invention to provide a device, for sealing pockmarks in a windshield, that requires a minimum of equipment; that takes a minimum of time; that does not need an external bracing system; that does not require a succession of pressure changes nor heat cycles; that does not require extensive vibration; and that provides a constant, controlled pressure on the apex of the conical fracture during the operation.